A semiconductor element is generally manufactured by forming a pattern on a wafer through a photolithography process. More specifically, the semiconductor element is manufactured by forming a photoresist film on a wafer, forming a photoresist pattern by exposing and developing the photoresist film, and etching a silicon film formed on the wafer using the photoresist pattern.
For the photolithography process performed in the semiconductor manufacturing process, the surface of the wafer is etched after a photoresist is coated. A process of removing the photoresist remaining after the etching process is referred to as an ashing process, and removal of the remaining photoresist is mostly accomplished in a chemical method.
If the remaining photoresist is not completely removed, a problem of generating an additional defect occurs in a secondary process, and thus the ashing process is regarded as one of the most important parts in the semiconductor manufacturing process.
A chemical wet ashing process of the prior art has a problem in that it should diversely respond in accordance with the application characteristic of a photoresist used in a coating, and there are various problems as described below.
Looking into conventional techniques, Korean Laid-opened Patent No. 10-2004-0098751 specifies a separation liquid which can remove a modified and hardened resist within a short time period at a high or low temperature by adding a separation accelerator as well as a water-soluble organic amine, a polar solvent and a corrosion inhibitor. Korean Laid-opened Patent No. 10-2006-0024478 specifies a photoresist separation liquid composition which does not cause further corrosion of metal wires although an isopropyl alcohol (IPA) rinsing process is omitted and, in particular, significantly improves a separation force by applying a photoresist separation liquid composition containing a cyclic amine, a solvent, a corrosion inhibitor and a separation accelerator. Japanese Laid-opened Patent No. JP2006072083A discloses a technique capable of performing separation at a room temperature on a thermally hardened resist, as well as a general resist, by using phosphoric ester and dissolved ozone.
However, the separation solution disclosed in Korean Laid-opened Patent No. 10-2004-0098751 falls short of an effect of suppressing corrosion of a metal wire, and the separation solution disclosed in Korean Laid-opened Patent No. 10-2006-0024478 does not have a sufficient separation force for a resist created in a severe condition such as a dry etching residue since a cyclic amine is used, and the separation solution of Japanese Laid-opened Patent No. JP2006072083A is disadvantageous in that a metal film at a lower portion is highly probable to be corroded due to the dissolved ozone.
Furthermore, the chemical wet ashing method inevitably uses various chemicals and thus has fundamental problems such as environmental problems, maintenance cost and the like. In addition, although it has been tried much to solve the problems recently as described above, performance of removing the resist still has much to be improved.